Both thermostats changed but temperature takes ages to get to 90

[Dave_d]

Hi guys, had main and in-line changed on Monday. The temperature of the car heaters have increased faster, however the gauge still only reads 70degrees by the time I get to work, 11 mile trip of mixed driving. Any ideas why?

[lukemk5gti]

Do you have a DSG?

Some of them have a second inline thermostat. Identical part though to the other one.

I replace mine and it's at 90 in I think 6miles or 6mins whichever comes first

I've never heard a report of replacing them and not fixing this issue.

Are you sure you trust the garage and that they did it?

If so, could be signal back to the dial but that wouldn't hold true considering it does eventually reach 90

[Dan_FR]

Genuine thermostats from VW?

My car will get up to 90 within 2-3 miles tops if I don't have the heaters on, obviously longer if I do.

It could also be your temp sensor. Few questions:- after your 11 miles to work, at the heaters 'hot hot' or 'luke to mildly' warm? Have you had the temperature checked over OBD as the temperature reading shown on the clocks is not a true display of the temperature

[Dave_d]

Yeah it’s a 2007 dsg. The garage rang vw who used my chassis number to get correct parts etc. Said there is 2 on my car. Inline and main, both genuine parts. After 11 miles I’m very toasty in the car, my heaters have never felt so warm haha. I have the heaters on when I’m on my way to work. I’ll try without tomorrow if it’s not too fresh. Not checked the temperature via obd. 

[Octoparrot]

Sorry to butt in but something's puzzling me. Where would diagnostics get a temp reading from? If it's the coolant temp sensor (is there only 1?) and that was giving false (low) readings how could you get an accurate idea if it's the thermostat sticking open or the temp sensor that's the problem? 

[Pesky jones]

I think the point is the gauge is not a true reflection of the temperature. Most gauges will read 90 once it hits 70

[Dan_FR]

If the heaters are plenty warm but the gauge is showing 70, you likely need a new temp sensor

Sorry to butt in but something's puzzling me. Where would diagnostics get a temp reading from? If it's the coolant temp sensor (is there only 1?) and that was giving false (low) readings how could you get an accurate idea if it's the thermostat sticking open or the temp sensor that's the problem? 

Dash reading only gives an indication, it lies to you to stop Joe Blogs panicking at small fluctuations and returning the car to the dealer when there is nothing wrong. For the Dash to read 70, the actual temp as measured by the sensor will be more like 60 degrees C which is why I would advise to check it...... as you wont have toasty hot heaters with a coolant temp of just 60 degrees C

[Octoparrot]

So how do you know or test to determine if the temp sensor is working properly?

[pudding]

VCDS or some other scan tool, or the hidden menu on the climate control apparently, but I've never used that.

VCDS takes the reading directly from the temp sensor, which is fitted into the main thermostat housing.   

The Dash gauge takes the same reading, but manipulates it as described above.   80 - 100 has been fudged to always be 90 on the gauge.

At this time of year when cruising on the motorway, the water temp will be in the mid 80s with working stats.

[Octoparrot]

Thanks for replying, so that relies on the temp sensor give correct outputs, how many sensors are there? I thought there was only 1 at the chain end of the engine?

[pudding]

I think there's 2, one on the stat as already mentioned, and one in the post radiator circuit somewhere.  Someone else will confirm.  DSG may even have 3 of the buggers!

[doylebros]

This is well worth a read:-

http://www.mk5golfgti.co.uk/forum/index.php/topic,78341.0.html